Thermal Aspects of Kumada Rearrangement in Symmetrical and Asymmetrical Polysilanes-Interdependence of Molecular Structure, Thermal Degradation, and Stability

Abstract

Thermal degradation behavior, exothermic patterns, and kinetic parameters of symmetrically/asymmetrically substituted polysilanes during the kumada thermal rearrangement in the temperature range of 100–450 °C, were investigated applying thermogravimetric (TGA) and differential scanning calorimetric (DSC) techniques. Three kinds of polysilanes, viz., Polydimethylsilane (PDMS), Polydiphenylsilane (PDPS) and Polymethylphenylsilane (PMPS) were synthesized through Wurtz/Wurtz-Fittig polycondensation. As-synthesized polysilanes were then characterized by FT-IR, CHNO, and TGA–DSC techniques. FT-IR spectra confirmed the presence of methyl, phenyl, and a combination of methyl-phenyl functional groups in PDMS, PDPS, and PMPS, respectively. From CHNO analysis, the chemical/empirical formula of PDMS, PDPS, and PMPS was found to be SiC2.01H6.25, SiC12.50H10.26, and SiC6.45H7.76, respectively. TGA results confirmed that PDPS was more thermally stable as compared to PDMS and PMPS. The kinetic parameters of polysilanes were determined by using isoconversional methods such as Ozawa and modified Kissinger–Akahira–Sunose (KAS) methods. The average value of activation energy for PDPS obtained from Ozawa and KAS methods was found to be 1078.49 and 1068.32 kJ/mole, respectively, which is very much higher as compared to that of PDMS and PMPS.